To determine whether cells are neoplastic we plan to develop a method that is based on the ability of cells to grow in the presence of certain drugs that preferentially stop growth of untransformed cells. We have found that these drugs in vitro arrest proliferation of untransformed BHK cells in G1. They partly arrest CHO cells, which show some of the characteristics of transformed cells. They do not arrest polyoma-transformed BHK cells in G1. The research would consist of testing a number of known cell lines for resistance to various concentrations of these drugs. If there is a general correlation between degree of transformation (determined by other putative in vitro tests, and by malignancy in vivo) and the requirement for a high concentration of drug to stop growth, we will have the basis for a quantitative test of transformation. The second phase of the work would be to obtain new chemically transformed cell lines and compare their sensitivities to the drugs in relation to their degree of malignancy. We would like to do these experiments with both fibroblastoid and epithelioid cells. BIBLIOGRAPHIC REFERENCES: Arthur B. Pardee and David S. Schneider (1977). "Control of Cell Growth in Cancer" Chemistry 50: 25-29. Arthur B. Pardee and Robert D. Dubrow (1977). "Control of Cell Proliferation" Cancer. In press.